add privacy page as standalone SPA view outside slide navigation

- New Kirby template/blueprint/JSON for privacy page (confidentialite slug)
- Standalone page state in slides store + router handling for non-nav pages
- Privacy.svelte view with background image, text blocks, footer
- Centralize vertical lines in App.svelte as fixed elements with per-slide visibility
- Footer privacy link language-aware (FR/EN)
- Portfolio mockup fix: read from default language for consistent EN display
- menu.php: add privacy page to Kirby panel navigation

refs #44

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/router/index.js

@@ -64,7 +64,12 @@ async function loadSlide(path) {
       siteInitialized = true;
     }
 
-    slides.setData(slidePath, data);
+    const finalIdx = slides.getIndexByPath(slidePath);
+    if (finalIdx !== -1) {
+      slides.setData(slidePath, data);
+    } else {
+      slides.setStandalone(data);
+    }
   } catch (error) {
     console.error(`[router] Failed to load slide ${slidePath}:`, error);
     slides.setLoading(slidePath, false);
@@ -95,21 +100,26 @@ export function slideTo(path, { skipHistory = false } = {}) {
   const idx = findSlideIndex(path);
   const slidePath = idx !== -1 ? slides.all[idx].path : path;
 
-  if (idx !== -1 && slides.all[idx].title) {
-    document.title = `World Game - ${slides.all[idx].title}`;
-  }
+  if (idx !== -1) {
+    slides.clearStandalone();
 
-  // Si on navigue vers la slide déjà active (ex: clic sur "Blog" depuis un article),
-  // déclencher popstate pour que la vue puisse réagir au changement d'URL.
-  if (idx === slides.activeIndex && !skipHistory) {
-    window.dispatchEvent(new PopStateEvent('popstate'));
-    return;
-  }
+    if (slides.all[idx].title) {
+      document.title = `World Game - ${slides.all[idx].title}`;
+    }
 
-  slides.slideTo(slidePath);
+    if (idx === slides.activeIndex && !skipHistory) {
+      window.dispatchEvent(new PopStateEvent('popstate'));
+      return;
+    }
 
-  if (idx !== -1 && !slides.all[idx].loaded) {
-    loadSlide(slidePath);
+    slides.slideTo(slidePath);
+
+    if (!slides.all[idx].loaded) {
+      loadSlide(slidePath);
+    }
+  } else {
+    // Page standalone (hors navigation)
+    loadSlide(path);
   }
 }